Standardize positioning attribute values to use `start` and `end` vs `after` and `before`

[eljefe223]

Environment Information

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• Browser and OS versions: (fill this out if relevant)

Describe the issue:

For controls that have positioning attributes, ie LabelPosition or IconPosition we are inconstant in the language we use to describe where an element will layout. In some cases, we use start and end and in others we use before and after. We should standardize on start and end which is more consistent with CSS and localization properties and values like flex-start or margin-inline-start

Before and After https://react.fluentui.dev/?path=/docs/components-switch--docs#label

Start and End https://react.fluentui.dev/?path=/docs/components-accordion--docs#expand-icon-position

Actual behavior:

We are not consistent with language used.

Expected behavior:

BE consistent with language used.

If applicable, please provide a codepen repro:

Priorities and help requested (not applicable if asking question):

Are you willing to submit a PR to fix? (Yes, No)

Requested priority: (Blocking, High, Normal, Low)

Products/sites affected: (if applicable)

[TristanWatanabe]

This valid as our positioning prop values do contain inconsistencies (see below). Fixing these to be consistent across the board in v9 would be a breaking change but this is possibly a good RFC candidate for a naming pattern to follow for new components and beyond (v10 etc.).